Core Release System and Method

ABSTRACT

A core release system  10  has a housing  28  provided with an impact member  30  arranged to impact a core sample  16  gripped in a core tube  12.  The housing  10  can be fitted over an end of the core tube  12  in which a core sample is gripped. The impact member is arranged to deform in preference to the core sample  16.  By applying a force to the housing  28  or the tube  12  which causes impact of the core sample  16  on the impact member  28  the core sample is displaced relative to, and released from the grip of, the tube  12.

Cross-Reference to Related Applications

This application claims priority from Australian Application No. 2015904439 filed Oct. 29, 2016, which is hereby incorporated herein by reference in its entirety.

TECHNICAL FIELD

A core release system and method is disclosed for facilitating the removal of a core sample from a tube such as core lifter case or like mechanism.

BACKGROUND ART

During core drilling (also known as diamond drilling) an inner core tube assembly is releasably locked at a downhole end of a core drill. The inner core tube assembly includes a core tube and a core lifter assembly fitted to an end of the core tube. The core lifter assembly comprises a core lifter case and a core lifter spring. An outer circumferential surface of the core lifter spring and an inner circumferential surface of the core lifter case are formed with a complementary taper. As a result of the tapered surfaces, relative axial motion between the spring and the case results in a reduction or increase in the inner diameter of the core lifter spring.

During drilling as a core sample is cut it progresses through the core lifter spring and core lifter case and into the core tube. Due to the orientations of the tapered surfaces on the spring and the case, the spring is displaced into an up-hole region of the core lifter case allowing it to expand radially to the extent necessary to allow the core sample to travel into the core tube.

During a core break the drill string is lifted in an up-hole direction. This causes the core lifter spring to move in a downhole direction relative to the core lifter case so that the tapered surfaces act to clamp the core lifter spring onto an outer circumferential surface of the core sample. This grips the core sample and transmits the upward pulling force onto the core sample breaking it from the adjacent strata.

The inner core barrel assembly can now be retrieved typically using a wire line. In order to allow inspection of the core sample it must be removed from the core tube. Usually the core sample is tightly gripped in the core lifter case by the core lifter spring. To release the grip it is necessary to displace the core lifter spring so as to travel within the core lifter case to a location where the taper of the case enables the core lifter spring to resiliently expand to release its grip on the core sample.

Prior to taking this step a geologist will often mark a portion of the outer surface of the core sample which protrudes from the core lifter case with an indication of the location of a specific bearing such as the bottom of a hole. This is often done by use of a pencil or scratching tool.

A common technique for displacing the core lifter spring to release the sample form the core lifter case is to strike a protruding portion of the core sample with a hammer. In an alternate technique the core tube with the attached core lifter assembly can be dropped onto the ground or impacted with a solid surface with the core sample leading.

While these techniques do result in releasing the core sample from the grip of a core lifter case they also often result in damaging or breaking of the end of the core sample. This may also or alternately result in the loss of the orientation reference from the core sample.

The above Background Art is not intended to limit the application of the system and method as disclosed herein.

SUMMARY OF THE DISCLOSURE

In one aspect there is disclosed a core release system comprising: a housing provided with an impact member, the housing capable of receiving an end of a tube in which a core sample is gripped, the system arranged so that on applying a force to cause impact between the core sample and the impact member the core sample is displaced relative to the tube.

In one embodiment the impact member is arranged to deform in preference to the core sample.

In one embodiment the impact member comprises a material which is softer than material constituting the core sample.

In one embodiment impact member is configured to fit within the tube.

In one embodiment impact member is provided with an impact face configured to impact with the core sample at a location inboard of a circumferential peripheral edge of the core sample.

In one embodiment the impact member includes a shock absorbing mechanism.

In one embodiment the impact member is movably mounted on the housing wherein the force displaces the impact member relative to the housing.

In one embodiment the housing is arranged to enable self-supported coupling to the tube.

In one embodiment the system comprises a coupling mechanism arranged to facilitate coupling of the housing with the tube enabling the housing to be self-supported on the tube.

In one embodiment the coupling mechanism is arranged to allow the housing to move relative to the tube in response to application of the force.

In one embodiment the coupling mechanism includes one or more magnets provided on one or both of the housing and the tube.

In one embodiment the coupling mechanism comprises a resilient member configured to act between an inside surface of the housing and an outer surface of the tube.

In one embodiment the resilient member comprises an O-ring supported inside of the housing.

In one embodiment the coupling mechanism comprises a cam lock mechanism arranged to operate by relative rotation between the housing and the core lifter case.

In one embodiment the system comprises a visual indicator arranged to provide a visual indication to a user of the system of an amount of displacement of a core sample into the tube subsequent to being impacted with the impact member.

In one embodiment the visual indicator is a window formed in the housing at a location enabling viewing of the impact member.

In one embodiment the window is further configured to enable visualisation of the tube at least when impact between the core sample and the impact member has displaced the core sample into the tube a distance sufficient to release sample from the grip of the tube.

In one embodiment the window and the impact member are arranged so that when the core sample has been displaced the sufficient distance only the core tube is visible through the window.

In one embodiment the housing comprises a sleeve and a cap demountably coupled to an end of the sleeve, the impact member being coupled to the cap.

The tube in relation to which the disclosed system may be applied includes but is not limited to: a core lifter case; a core tube; and, a core tube to which a core lifter case is attached.

In another aspect there is disclosed a method of releasing a core sample from a tube, the method comprising: locating a housing over an end of the tube in which a core sample is gripped; and impacting the core sample with an impact member carried by the housing.

In one embodiment the method comprises arranging the impact member to deform when impacted by the core sample.

In one embodiment the method comprises forming at least a portion of the impact member from a material that is softer than the core sample.

In one embodiment the method comprises configuring the impact member to fit inside of the tube.

In one embodiment the method comprises impacting the core sample with the impact member at a location inboard of a circumferential peripheral edge of the core sample.

In one embodiment locating the housing over an end of the tube comprises coupling the housing to the tube in a self-supporting manner.

In one embodiment coupling the housing comprises magnetically coupling the housing to the tube.

In an alternate embodiment coupling the housing comprises mechanically coupling the housing to the tube.

In one embodiment the method comprises providing a visual indicator indicative of an amount of displacement of the core sample into the tube as a result of the impacting.

In one embodiment the impacting comprising repeatedly impacting the core sample with the impact member until the visual indicator provides an indication that the core sample has been displaced a distance sufficient to release the core sample from the grip of the tube.

In one embodiment impacting comprises dropping, knocking or thrusting the core tube with the coupled housing onto a surface in a manner wherein an end of the housing contacts the surface.

The tube in relation to which embodiments of the disclosed method may be applied can include but is not limited to: a core lifter case; a core tube; and, a core tube to which a core lifter case is attached

One embodiment the disclosed system may comprise: a housing provided with an impact member, the housing being capable of self-supported coupling to an end of a tube in which a core sample is gripped, the system arranged so that on applying a force to cause impact between the core sample and the impact member the core sample is displaced relative to the tube.

Another embodiment of the disclosed system may comprise: a housing provided with an impact member, the housing capable of receiving an end of a tube in which a core sample is gripped, the system arranged so that on applying a force to cause impact between the core sample and the impact member the core sample is displaced relative to the tube; and a visual indicator arranged to provide a visual indication to a user of the system of an amount of displacement of a core sample into the tube subsequent to being impacted with the impact member.

BRIEF DESCRIPTION OF THE DRAWINGS

Notwithstanding any other forms which may fall within the scope of the system and method as set forth in the Summary, specific embodiments will be now described by way of example only with reference to the covering drawings in which:

FIG. 1 is a section view of a representation of the disclosed core release system together with a section view of a lower end of a core tube and associated core sample;

FIG. 2 is a section view of the core removal system when self-supported on an end of the core tubes;

FIG. 3 is a side view of a housing of the core release system prior to operation of the core release system to release the core sample;

FIG. 4 is a section view of the core release system, core tube and core sample subsequent to operation of the core release system to release the core sample from the core tube; and

FIG. 5 is a side view of the housing of the core release system upon operation as shown in FIG. 4.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENT

FIGS. 1 and 3 depict a section and side view respectively of an embodiment of the disclosed core release system 10. In FIG. 1 the core release system 10 is shown in conjunction with a section view of a tube in the form of a core tube 12 fitted at a lower end with a core lifter assembly 14 and captured core sample 16. The core lifter assembly 14 comprises a core lifter spring 18 which is located inside a core lifter case 20. The core lifer case 20 is screwed onto an end of the core tube 12.

The core sample 16 is firmly gripped by a core lifter spring 18 which acts as a wedge between the core sample 16 and an inner tapered surface 22 of a core lifter case 20. The core sample 16 is also shown with a representation of bottom of hole mark 24 applied to an outer surface at an exposed end 26 of the core sample 16.

In order to release the core sample 16 from the core lifter case 20 and the assembly 14 it is necessary to displace the core lifter spring 18 relative to the case 20 so that the spring 18 resides in a widened inner diameter portion of the case 18 created by the tapered surface 22. In the prior art this is often achieved by hitting the end 26 of the core sample 16 with a hammer. This displaces the core sample 16 together with the core lifter spring 18 in the direction of the tube 12 thereby releasing the grip of the spring 18. However as previously described this can and often does damage the end 26 including to the extent of losing the bottom of hole position reference mark 24.

Embodiments of the disclosed core release system 10 provide an alternate way for releasing a captured core 16 in a manner which minimises damage to the core sample 16 while also enhancing safety in the removal process.

The core release system 10 comprises a housing 28 provided with an impact member 30. Some embodiments of the system 10 are arranged so that the housing 28 is capable of self-supported coupling to the core lifter case 20. The coupling may be directly on the or to the case 20 or alternately on or to the core tube 12 to which the case 20 is attached. This is shown for example in FIG. 2.

By being coupled in a self-supporting manner the system 10 can be retained on an end of the core tube 12 while the core tube 12 is being handled or otherwise manipulated without the need for an operator/user physically holding the housing 28. Thus for example the core tube 12 with the coupled self-supported system 10 can be lifted or held vertically off the ground with the system 10 lower most without it falling off. This arrangement is shown for example in FIG. 2.

By being self-supporting the system 10 has an inherent level of safety over use of say a hammer to release a core sample. Using a hammer is problematic as it can lead to injury when for example the hammer skids off or rebounds from the core sample 16. Also by being self-supporting a user need not hold the system 10 onto the end of a core tube 12 while also trying to hold onto and manipulate the core tube itself. Trying to do so would not only be awkward with an industry standard three meter long core tube 12, but it would be dangerous with the chance of impact an operator's hand if the two items misaligned, or if a flying rock chip hits the operator's eye due to the head of the operator being in close proximity to the impact point.

The system 10 is arranged so that on applying a force to cause impact between the core sample 16 and the impact member 30 the core sample 16 is displaced relative the core lifter case 20. More particularly the sample 16 is displaced in a direction further into the case 20, i.e. in the direction of the core tube 12. The force is applied along a central axis 32 of the tube 12 and the coupled system 10. The force may be applied from the side of the tube 12 shown as force F1 in FIG. 2; or from below the housing 28/impact member 30 shown as force F2 in FIG. 2.

Of course, irrespective of the direction of application the other force will be automatically generated as an equal and opposite force in accordance with Newton's third law of motion. Most conveniently, the force is applied by holding the core tube 12 with the system 10/housing 28 coupled to the case 20 and then driving tube 12 with the housing 28 first onto a firm surface. The firm surface could be for example the ground or a mine wall. This action may be required to be repeated several times in order to fully release the core sample 16 from the case 20.

In order to prevent or at least minimise damage to the end 26 of the core sample 16 the impact member 30 is arranged to deform or otherwise absorb energy in preference to the core sample 16. The deformation of the impact member 30 may be result of a property of the material from which the member 30 is made and/or by the provision of a shock absorber. For example the material may be one which is elastically or plastically deformable; or in the case of a shock absorber, may include a mechanical spring or a layer or portion of resilient material between an upper face 34 of the impact member 30 and the housing 28. In the present embodiment the impact member 30 comprises a rubber block 36 mounted on top of a block 38 made from a plastics material. The rubber block 36 in this instance deforms on impact with the core sample 16.

The impact member 30 is configured to fit within the core tube 12. This is shown for example in FIG. 4. As explained later this enables the impact member to enter the core lifter case 20 during operation of the system 10. Further the face 34 of the impact member 30 is configured to impact with the core sample 16 at a location inboard of a circumferential peripheral edge of the core sample 16. Thus no impact force is applied to the peripheral circumferential edge of the sample 16. Rather all the impact force is directed to a central region of the core sample 16. This assists in minimising or totally avoiding any damage to the sample 16 including fracturing.

The system 10 has a coupling mechanism 40 arranged to facilitate coupling of the housing 28 with the core tube 12 enabling the housing 28 to be self-supported on the core tube 12. In this embodiment the coupling mechanism 40 is also arranged to enable the impact member 30 to move linearly relative to the case 20 in response to application of the force. In this particular embodiment this is achieved by providing the coupling mechanism 40 as one or more magnets 42. The magnets 42 are embedded in a cylindrical wall 44 of the housing 28. The inner diameter of the wall 44 is greater than the outer diameter of the case 20 so that there is or can be a small annular gap created there between. This assists in minimising friction and enabling easy movement of the system 10 and more particularly the impact member 30 relative to the case 20.

The system 10 is provided with a visual indicator 46 which is arranged to provide a visual indication to a user of the system 10 of an amount of displacement of the core sample 16 relative to and more particularly into the core lifter case 20. In this particular embodiment the visual indicator 46 comprises a plurality of windows 48 formed in the cylindrical wall 44 of the housing 28. The windows 48 are located to enable viewing of the impact member 30 before the system 10 is coupled to the case 20 and/or when coupled but prior to application of the impact force.

FIGS. 2 and 3 illustrate the relative juxtaposition of the system 10 and case 20 when coupled together but prior to application of an impact force. In this juxtaposition the face of the sample 16 may be abutting or very close to the face 34 of the impact member 30. A person utilising the visual indicator 46 viewing through the window 48 will be able to see the impact 30. This indicates that there has been no displacement of the core sample 16 relative to the casing 20.

FIGS. 4 and 5 on the other hand illustrate the juxtaposition of the system 10 and case 20 after one or more applications of the impact force. When the impact force is applied the core sample 16 and lifter spring 18 are initially moved together relative to the case 20 in a direction into the tube 12. As this occurs the downhole end of the casing 20 moves over the impact member 30 as the impact member 30 moves into the case 20. As a result the impact member 30 is progressively covered by the casing 20. Thus now the case 20 is visualised through the window 48.

The impact member 30 is dimensioned so that it's complete shrouding by the case 20 as shown in FIGS. 4 and 5 is indicative of the spring 18 and sample 16 being displaced a sufficient distance to enable the spring 18 to expand radially outward so as to release the grip of the core 16 to the case 20. Thus in use a user will apply the impact force for as many times as required so that the impact member 30 is fully covered by the case 20. This can be visualised through the window 48 and provides an indication that the core sample 16 has been released from the grip of the core lifter assembly 14.

Whilst a specific system and method embodiment have been described it should be appreciated that the system and method may be embodied in many other forms. For example the attachment mechanism 40 is described as comprising one or more magnets 42. However alternate coupling mechanisms may be used. These include for example, but not limited to, one or more resilient members that act between the housing 28 and the case 20 and/or tube 12 to provide a friction fit or coupling there between. A specific example of this is a rubber O-ring retained in the inner circumferential surface of the housing 28. A further alternative is forming the coupling mechanism 40 as a cam lock system. This may operate by rotating for example the housing relative to the case 20/tube 12.

Further, it should be understood that it is not absolutely necessary for the housing 28 to be coupled in a manner that allows it to move relative to the case 20. In order to transmit the impact force all that is required is for the impact member 30 to move relative to the case 20. This may be achieved for example by, with reference to FIG. 4, mounting the impact member 30 on a post 60 which extends through the base 50 so that the impact member 30 can slide in axial direction of the post 60 relative to the housing 28. The post 60 is provided with an impact plate 62 at one end with a spring 64 being retained between the plate 62 and the base 50. Thus in this embodiment the housing 28 can be coupled to the case 20 and/or tube 12 with the impact member 30 butting or closely adjacent to the end 26 of the core 16 as shown in FIG. 2.

The use of this modified embodiment of the system 10 is the same as described above the only difference being now that the impact force causes the impact member 30 to lift off the inside surface of the base 50 in order to displace the spring 18 and core 16. In this embodiment the visual indicator may simply comprise the juxtaposition of the plate 62 to base 50. In particular the post 60 can be dimensioned so that the abutment of the plate 62 with the base 50 provides the visual indication that the core 16 has been released from the case 20.

Additionally when the impact member 30 comprises a layer or portion of resilient material between an upper face 34 of the impact member 30 and the housing 28, it is not essential that the resilient material is upper most and constitutes the face 34. For example it is possible for the block 38 to be mounted on top of the rubber block 36. In such an embodiment the face 34 would be constituted by the block 38. Nonetheless the impact member 30 still provides protection to the core sample 16 by action of the resilience and shock absorbing properties of the rubber block 36.

The described embodiments of the core release system and method are described in the context of core drilling where the tube can be considered to be the core tube, the core lifter case or the ensemble of a core tube and a core lifter case. However the disclosed system and method may be applied and used without modification to any tube in which a core sample or indeed any article is gripped in a way where the grip can be released by linearly moving the article relative to the tube.

In the claims which follow, and in the preceding description, except where the context requires otherwise due to express language or necessary implication, the word “comprise” and variations such as “comprises” or “comprising” are used in an inclusive sense i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the system and method as disclosed herein. 

What is claimed is:
 1. A core release system comprising: a housing provided with an impact member, the housing capable of receiving an end of a tube in which a core sample is gripped, the system arranged so that on applying a force to cause impact between the core sample and the impact member the core sample is displaced relative to the tube.
 2. The system according to claim 1 wherein the impact member is arranged to deform in preference to the core sample.
 3. The system according to claim 1 wherein the impact member is configured to fit within the tube.
 4. The system according to claim 1 wherein the impact member is provided with an impact face configured to impact with the core sample at a location inboard of a circumferential peripheral edge of the core sample.
 5. The system according to claim 1 wherein the impact member comprises a shock absorbing mechanism.
 6. The system according to claim 1 wherein the impact member is movably mounted on the housing wherein the force displaces the impact member relative to the housing.
 7. The system according to claim 1 wherein the housing is arranged to enable self-supported coupling to the tube.
 8. The system according to claim 7 comprising a coupling mechanism arranged to facilitate coupling of the housing with the tube enabling the housing to be self-supported on the tube.
 9. The system according to claim 8 wherein the coupling mechanism is arranged to allow the housing to move relative to the tube in response to application of the force.
 10. The system according to claim 8 wherein the coupling mechanism comprises: (a) one or more magnets provided on one or both of the housing and the tube; or (b) a resilient member configured to act between an inside surface of the housing and an outer surface of the tube; or (c) a cam lock mechanism arranged to operate by relative rotation between the housing and the core lifter case.
 11. The system according to claim 10 wherein the resilient member comprises an O-ring supported inside of the housing.
 12. The system according to claim 1 comprising a visual indicator arranged to provide a visual indication to a user of the system of an amount of displacement of a core sample into the tube subsequent to being impacted with the impact member.
 13. The system according to claim 12 wherein the visual indicator comprises a window formed in the housing at a location enabling viewing of the impact member.
 14. The system according to claim 13 wherein the window is further configured to enable visualisation of the tube at least when impact between the core sample and the impact member has displaced the core sample into the tube a distance sufficient to release sample from the grip of the tube.
 15. The system according to claim 14 wherein the window and the impact member are arranged so that when the core sample has been displaced the sufficient distance only the core tube is visible through the window.
 16. The system according to claim 1 wherein the housing comprises a sleeve and a cap demountably coupled to an end of the sleeve, the impact member being coupled to the cap.
 17. The system according to claim 1 wherein the tube comprises: a core lifter case; or, a core tube; or a core tube to which a core lifter case is attached.
 18. A method of releasing a core sample from a tube, the method comprising: locating a housing over an end of the tube in which a core sample is gripped; and impacting the core sample with an impact member carried by the housing.
 19. The method according to claim 18 comprising arranging the impact member to deform when impacted by the core sample.
 20. The method according to claim 19 comprising configuring the impact member to fit inside of the tube.
 21. The method according to of claim 18 comprising impacting the core sample with the impact member at a location inboard of a circumferential peripheral edge of the core sample.
 22. The method according to claim 18 wherein locating the housing over an end of the tube comprising coupling the housing to the tube in a self-supporting manner.
 23. The method according to claim 22 wherein coupling the housing comprises (a) magnetically coupling the housing to the tube; or (b) mechanically coupling the housing to the tube.
 24. The method according to claim 18 comprising providing a visual indicator indicative of an amount of displacement of the core sample into the tube as a result of the impacting.
 25. The method according to claim 24 wherein the impacting comprising repeatedly impacting the core sample with the impact member until the visual indicator provides an indication that the core sample has been displaced a distance sufficient to release the core sample from the grip of the tube.
 26. The method according to claim 18 wherein the tube comprises: a core lifter case; or, a core tube; or a core tube to which a core lifter case is attached. 